1. Field of the Invention
The present invention relates to an externally activated input shaft clutch brake having a clutch pedal that simulates the feel of the engagement of a clutch brake that has a mechanical linkage.
2. Background Art
Clutches for multi-speed transmissions generally include a release bearing that disengages the clutch to permit the transmission to be shifted between gears. Some hydraulic clutch release systems may be synchronized by synchronizing systems that match shaft speeds. Non-synchronized transmissions do not require synchronizers, but may benefit from an input shaft brake, especially for first gear and reverse gear engagement.
Non-synchronized transmissions may be provided with a wear compensating hydraulic release system and cannot use economical prior art clutch designs. Pneumatic, hydraulic, electric or internal transmission brake-control systems have been proposed that use an external activation system to energize an input shaft clutch brake.
External activation clutch brakes (EACB) can be triggered by many different methods. The simplest method of triggering an EACB is an electrical switch. Other methods of triggering an EACB may include pneumatic or hydraulic valves and the like. An intelligent brake control system may include input systems from the following sources: clutch pedal release; transmission in neutral; vehicle road speed; engine rpm; transmission input shaft rpm; engagement time; or clutch brake torque.
Any or all of the above inputs can be used in the control of a clutch brake. The advantages of an intelligent brake control system include the control of the length of engagement time, engagement only when the vehicle is not moving, engagement only when the transmission is in neutral, engagement only when the clutch pedal is suppressed, or engagement only when two or more of the above conditions are present. Prior art clutch brake engagement timing may be affected by a self-adjusting clutch mechanism.
FIG. 1 illustrates a conventional “pull-type” clutch 10 for a non-synchronized transmission system. A clutch pedal 12 is shown in conjunction with a portion of a truck cab floor 14 toward which the clutch pedal 12 is moved to disengage the clutch. A clutch release linkage 18 is diagrammatically shown to include a plurality of links and mechanical pivots. The clutch release linkage 18 transfer movements of the clutch pedal 12 to a clutch release bearing 20. The clutch release bearing 20 is disposed between an engine 22 that provides torque and an input shaft clutch brake 24. The input shaft clutch brake 24 engages a bearing cap 26 of a transmission 28 to apply a braking force to the input shaft. The input shaft clutch brake 24 is adapted to stop rotation of the input shaft of the transmission 28 particularly when it is desired to shift the transmission between low range gears or between forward and reverse.
In conventional “pull-type” clutches for non-synchronized transmission systems, the clutch brake 24 may be keyed to an input shaft between the release bearing 20 and the bearing cap 26. When the clutch 10 is disengaged, the release bearing 20 disengages the driven disk and clamps the clutch brake 24 against the transmission bearing cap 26 causing the input shaft to slow until it stops rotating allowing the gears in the non-synchronized transmission to be changed without causing gear clash/damage and facilitating shifting into a new gear range.
The clamping action of the release bearing 20, clutch brake 24 and transmission bearing cap 26 causes an increase in the load required to depress the pedal 12 near the bottom of the pedal stroke. A driver feels this increase in load and realizes that the clutch brake 24 has been engaged. This increased load phenomenon is known as “clutch brake squeeze.” Drivers are familiar with the feel of a pedal 12 as it provides clutch brake squeeze and react to clutch brake squeeze by shifting the transmission only after such feedback is felt.
Conventional pull-type clutches generally include a mechanical linkage that transmits the pedal motion to the clutch release bearing linkage and in turn to the clutch release bearing and input shaft brake mechanism. Pneumatic, hydraulic, electric or internal transmission brake-control systems have been developed that may benefit from the use of an external activation system to energize clutch brakes. An external activation clutch brake may be actuated by a simple switch that is independent of the clutch release bearing position. The switch can be located at various positions in the clutch release linkage or on the transmission. The output of such a switch may be combined with other vehicle switch outputs for controlling the input shaft brake.
There is a need for an external activation clutch brake that simulates the clutch brake squeeze feel of the release bearing load and increases the pedal force at the bottom of the pedal stroke. There is also a need for a clutch brake system that can be triggered by a simple switch or valve that can be used to control actuation of the clutch brake while simulating the feed of a conventional clutch brake.
These and other problems and needs are addressed by applicants' invention as summarized below.